Loops '07 was held in Morelia, Mexico. My has links to my slides and the accompanying audio.

Here are some talks I went to, and some personal impressions (these are just brief tiddlers to myself, please don't take them too seriously)

Monday
Lucien Hardy, The causaloid formalism: a tentative framework for quantum gravity
Compression of measurement data
Obtain probabilistic distribution over temporal orderings of measurements maybe?
Rafael Sorkin, Quantum reality and anhomomorphic logic
Wants to use a "quantum" version of probability by discarding preclusion or inference rules
discarding logical "and" (multiplication) and/or discarding logical "or" (addition)
Talked to him about complex probability distributions over paths.
John F. Donoghue, Effective field theory and quantum general relativity
He argued that the Effective Field Theory of gravity could be used to perturb around a Newtonian potential to get the classical (GR) corrections and the quantum GR correction proportional to -- in two different ways.
Quantum GR will have to reproduce this.
Rodolfo Gambini, Relational physics with real rods and clocks, (A)
Works with Jorge Pullin
Err, it was hard to understand what he was saying, and his talk was kind of scattered.
Johannes Tambornino, Taming observables in GR: A perturbative approach, (B)
Tries to quantize symmetry reduced theory the right way.
Frederic P. Schuller, Area metric gravity, (B)
Reformulate everything in terms of "area metric."
Merced Montesinos, Cartan's equations define a topological field theory, (B)
Main idea: include Riemann curvature and Torsion as independent degrees of freedom. Them put extra "topological" terms, like Euler characteristic and Pontryagin characteristic, in the action to ensure and satisfy Cartan equations.
Possibly related paper: http://arxiv.org/abs/gr-qc/0603076
Marat Reyes, Generalized path dependent representations for gauge theories, (B)
Rats, I missed this one.
Yuya Sasai, Braided quantum field theories and their symmetries, (A)
Err, very hard to tell what the heck he was doing since his English wasn't very good.
Garrett Lisi, Deferential Geometry, (A)
:) My talk went very well.
"This is very interesting." -- L.S. "It's not bullshit." -- S.H.
Tuesday
Thomas Thiemann, Elements of Loop Quantum Gravity
Has a new book coming out in September -- should be good.
Talk was packed full of good stuff.
Start wit Palatini formulation, combine constraints into master , convert variables to holonomies and fluxes, build solutions using coherent states, minimize expectation value of master constraint, , rather than making it strictly .
Abhay Ashtekar, LQG: Lessons from models
Symmetry reduced models. Spherically symmetric black holes, 1+1.
, Vertex amplitude and propagator in loop quantum gravity
Work in . Barrett/Crane model has problem with off diagonal (vertex) terms -- B.C. doesn't give intertwiners in perturbation calc. so it's wrong. Need to use GFT to get better model.
Jan Ambjorn, 4d quantum gravity as a sum over histories
His talk went long and he got cut off.
I'm kind of unimpressed with CDT -- it's an odd approximation that forces plausible numerical results.
Dan Christensen, Computations involving spin networks, spin foams, quantum gravity and lattice gauge theory (B)
Kind of odd: gets positive real values for QM amplitude of spinfoam areas.
Wade Cherrington, Numerical Spin Foam Computation of Pure Yang-Mills Theory (B)
YM on a lattice, in an odd way. Holonomies. Expand amplitudes into group characters.
Seth Major
Kodama state, approximating flat spacetime, from exponentiating Chern-Simons action.
John Swain, Spin Networks and Simplicial Quantum Gravity (B)
Cool guy. 3+1 D Regge -> simplicial, areas and angles.
Wednesday
Moshe Rozali, Background Independence in String Theory
No action for in string theory. Have to choose a metric and perturb around that.
Klaus Fredenhagen, General covariance in quantum field theory and the background problem in perturbative quantum gravity
Sited new Stefan Hollands paper on BRST and Yang-Mills in curved spacetime.
Path integral is not covariant when you define it in detail.
Admissible embeddings are ones that preserve causal curves.
Alejandro Perez, Regulator dependence in quantum gravity and non perturvative renormalizability: possible new perspectives
missed it to talk to S.H.
Martin Reuter, Asymptotically safe quantum gravity and cosmology
Missed it. :( I came down with flu. But watched it online.
Using truncated action, with running coupling constants and , there is a Gaussian fixed point at and a non-Gaussian fixed point, .
Using more action terms, with many running parameters, the EH action appears to emerge as the unique fixed point at high energy. Just comes from fields and symmetries.
Large cosmo constant at high energy can drive inflation, without inflaton.
His recent paper on this just came out.
No parallel sessions
Quarantined myself because of flu.
Thursday
Feeling better -- think I'll venture out of hotel room again.
Daniele Oriti, Group field theory: spacetime from quantum discreteness to an emergent continuum
G's live at vertices. Graphically beautiful slides -- equations and figures.
My guess on what GFT is: start with many copies of a Lie gp, G. State is a collection of reps for each gp. When these states "match" these gps are linked, giving a spin network approximating a base manifold for a principal G-bundle.
No, I talked with Thomas Thiemann and he said this isn't how it works. There is only a G for each dimension of the spacetime (e.g. four, or three for just space),
Artem Starodubtsev, Some physical results from spinfoam models
According to a discussion at Physics Forums, this talk will actually be about BF gravity.
He didn't show up to the conference. Had some travel holdup in the US.
Martin Bojowald, Loop quantum cosmology and effective theory
Skipped it to talk with L and S.
Jorge Pullin, Uniform discretizations and spherically symmetric loop quantum gravity
Sundance Bilson-Thompson, Braids, loops, and the emergence of the standard model (B)
Leader of the Braidy Bunch.
Poor guy had a plague of audio problems.
gluons are two stacked braids, with a plus and minus charge.
Jonathan Hackett, ribbon networks, (B)
reduced link invariants
Yidun Wan, ribbons, (B)
nice circle diagrams for tetra, and links could describe topology, but why are they braided?
Jonathan Engle, cosmology, (A)
Ileana Naish-Guzman, On the regularizability of the Ponzano-Regge model, (A)
Works with John Barrett. Soft Brittish accent. Twisted cohomology groups over a cell complex.
James Ryan, Aspects of Group Field Theory (A)
Excellent intro to GFT. with group su(1,1) or su(2)
Winston J. Fairbairn, Quantization of string-like sources coupled to BF theory: transition amplitudes and topological invariance, (A)
(d-3) branes.
Friday
Fotini Markopoulou, Quantum gravity and emergent locality
Quantum Graphity
Lee Smolin, Chiral excitations of quantum geometries as a possible route to unification
"New theories should include surprises."
Ribbons as framed graphs, consistent with a cosmological constant.
We don't really know the relationship between spin network Hamiltonian constraint and spin foam with evolution moves.
Working with Sundance's braids
Sabine Hossenfelder, Phenomenological Quantum Gravity
"Top down inspired bottom up approaches"
Pessimistic Freeman Dyson quote on QFT/GR independence.
Colider constraints on KK models. (Black hole production)
Zero black holes in standard setup (I'm not sure that's true).
Minimal length scale as UV cutoff. (Doesn't this relate to discrete deSitter modes?)
William Donnelly, Entanglement Entropy in Loop Quantum Gravity (B)
Black hole entropy. Spin networks as the boundary/horizon in two part spinfoam/spacetime.
Olaf Dreyer, Internal Relativity: A progress report (A)
Start with something like Ising model on lattice with Lorentz group as internal structure.
Florian Girelli, 2-Groups and Topological Action (changed talk title!) (A)
parallel transp of strings. defined 2-group, 2-Lie algebra, 2-principal bundle. Need 2-Peter-Weil theorem.
one of not many DSR talks...
Roberto Pereira, The loop-quantum-gravity vertex-amplitude (A)
Works with Rovelli.
Emanuele Alesci, Graviton propagator: the non diagonal terms (A)
Works with Rovelli. (I get the impression this guy does the grind work of the calculations.) on {10J} propogator.
Had to make up a term so that intertwiners would be involved when calculating the off diagonal part of the propogator.
Isabeau Premont-Schwarz, Quantum Evolution in an Expanding Hilbert Space (Talk title at last minute) (A)
Is this just using a non-square for evolution?
Saturday
John Stachel, Projective and Conformal Structures in General Relativity
Older guy. Einstein biographer.
Cecile deWitt has new book out, "Functional Integration"
Affine space, affine connection and curvature. Need to break geometric variables into smaller pieces before quantizing.
(His slides were messed up, missing most of the math symbols, which kinda wrecked it)
Michael Reisenberger, Canonical gravity with free null initial data
Free (unconstrained) gravitational initial data variables are known for initial hypersurfaces consisting of two intersecting null hypersurfaces. Recently the Poisson bracket on functions of such data has been obtained. This opens the prospect of a constraint free canonical formulation of general relativity.
David Rideout, Can the supercomputer provide new insights into quantum gravity?
Cactus. Causal sets and spin networks.

FQXi member -- might see the same talk in Iceland
(A,B) detiddlers which parallel session

During last two hours, questions were asked of the Plenary speakers, based on a book that had been passed around the audience. Carlo Rovelli moderated.

You're at Loops '17, presenting your talk. Presuming your research program has been fully successful, describe your talk. What likelihood do you estimate for this happening? (This question was saved until the end, so speakers could prepare.)
Topology change in QG?
Abhay: not possible in canonical framework, but possible in LQG spin network.
Does QG say anything about QM? Do we need a deeper framework, or a new interpretation, or different GR?
Lucien: Need new math.
John S: Need process QMI. (use paths)
Thomas Thiemann: No. (just use conservative approach)
Bianca: Relational framework
John D: Path integrals OK, need to change GR.
QG has fluctuating causal structure -- would this have any measurable effect?
Sabine: photon spreading
Michael: Matter sees only one spacetime. (yep)
What is finite in spin foam models?
Alejandro Perez: There are ambiguities in the theory.
What would be a graph theory of nature? Spinfoam fundamental, or embedded in a manifold?
Thomas: Topology change, so not embedded. He thinks spinfoam.
Sundance: Braids.
The first question was answered last:
Lucien: Causaloids.
John D: Background dependent, GR + SM emergent from spin substrate, with perturbative breaking of general covariance. 60%
Thomas T: Complete description of QGR, as well as experiments done by himself. (ha) 5%
Ashtekar: Resolution of all ambiguities in LQG, and establishment of all relationships between branches.
A Perez: Thiemann was wrong. (ha!) "We have to make the road by walking."
M Reuter: Same underlying theory, with non-Gaussian fixed point. 20%
Daniele:
100% - statistical GFT, with low temperature equilibrium phase
80% - derive effective dynamics from GFT
50% - one model singled out as successful
Sabine: her talk would have the same title (ha) Measurements to support one model or another.
New, unexpected data. 50%
She'd find a permanent position. (ha)
John S: Quantized Conformal Structures. But odds were low he'd be with it in 10 years. :(
David Rideout: Causel sets give QM and GR. Probability: epsilon. (ha)
Carlo Rovelli: closing words. "Let each of a hundred flowers bloom" -- quote from Michael's talk.

Random tiddlers:

Many people used Beamer for their slides.

Loops '08 will be in Nottingham, England, in July (unless I misheard?)
Loops '09 probably in Beijing (or maybe P.I.)

I met a LOT of people

PI grad students
Chanda
Jean Christian Boileau
Jonathan Hackett (social guy at the end of table)
Joel Brownstein (inflation guy)
Bruno Hartmann (skinny sharp german guy with glasses, works with Thiemann)
Isabeau Premont-Schwarz (funny german guy with glasses)
Sean (ultimate frisbee guy)
Cecilia
Alejandro Satz (http://realityconditions.blogspot.com/)
Joel Brownstein (inflation)
William Donnely (http://williamdonnelly.blogspot.com/)
other PI people
Lucien Hardy
Fotini
Olaf?
Lee Smolin
Sabine
Sundance
Hans Westman (big baldish german with glasses)
Rafael Sorkin
misc
John Stachel
Daniele Oriti
Alejandro Perez (kind of wild looking)
Florian Gireli
John Swain
Michael Reisenberger
Jonathon Engle
Wayne Bomstad (grad student, works with John Klauder in Florida, said he admires for being well rounded)

The whole landscape

No notes in this view